This invention relates to a fuel supply control method for an internal combustion engine, and more particularly to a fuel supply control method of this kind which is adapted to enrich a mixture to be supplied to the engine when the engine is operating in high load regions.
In an internal combustion engine provided with a fuel injection system in general, the valve opening period of fuel injection valves of the system is set to a value obtained by multiplying a basic value Ti read from a basic Ti map based upon absolute pressure within an intake pipe of the engine and engine rotational speed by various correction coefficients appropriate to operating conditions of the engine. When the engine is in a high load operating condition, the air/fuel ratio of a mixture to be supplied to the engine over the whole high load region is set to a certain value (e.g. 12.0) richer than a theoretical air/fuel ratio (14.7) by multiplying the basic value Ti by an enriching coefficient KWOT or by reading a value of the valve opening period of the fuel injection valves read from a WOT (wide-open-throttle) map specially provided for application in high load operation of the engine, to thereby obtain increased engine output required for such high load operation, as proposed by Japanese Provisional patent Publication (Kokai) No. 57-137633.
High load operating regions of an internal combustion engine include a certain region where engine knocking can easily occur. In such knocking-occurring region, the engine often undergoes knocking particularly when the engine temperature is high.
However, according to the above conventional methods, both of engine temperature and engine rotational speed are not taken into consideration in setting the enriching coefficient KWOT and the WOT map. As a result, these conventional methods are unable to prevent the occurrence of engine knocking during operation of the engine in the aforementioned knocking-occurring region while the engine temperature is high.